Michèle Beaconsfield

The term ectropion is derived from the Greek ek (away from) and tropein (to turn) and refers to any form of everted lid margin.

The eyelid margin position is dependent on the tension in the tarsus and the canthal tendons (Figure 3.1), supported by the orbicularis muscle. Spasm of the orbicularis, as may occur in new born infants, can cause spontaneous eversion of the lids. Ageing changes affecting the orbicularis muscle and the canthal tendons are the cause of involutional ectropion. This is aggravated by the laxity of the lower lid retractors. Tumours, such as meibomian cysts, may cause mechanical ectropion. Cicatricial ectropion is caused by a shortage of skin. This may be congenital, as in some patients with Down's syndrome, or acquired following trauma; it may involve the upper and/or the lower lid. In seventh nerve palsy and paralytic ectropion, the support normally provided by the orbicularis muscle is absent: the lower lid position is therefore dependent on the medial and lateral canthal tendons which stretch mechanically with time.

Although classifications are helpful, many ectropia are multifactorial. Thus what started

Medial Lateral

Medial Lateral

Figure 3.1 Lower lid margin elements. Tarsus and canthal tendons.

Figure 3.1 Lower lid margin elements. Tarsus and canthal tendons.

as a cicatricial ectropion, with shortage of skin, may progress to include stretching of the tarsus and canthal tendons. Only correcting the skin shortage may in itself be insufficient: a lid tightening procedure may be required, in addition to addressing the skin shortage, to adequately correct the ectropion. The most important factors to establish in corrective surgery are where and how the lid should be tightened or supported. This forms the basis of this chapter. The correction of other factors involved in ectropion repair is covered elsewhere, such as skin shortage (Chapter 2) and seventh nerve palsy (Chapter 7).

Ectropion is classified as:

• Congenital

- Involutional

- Mechanical

- Cicatricial

- Paralytic

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